Search results for "density of states"

showing 6 items of 186 documents

Supercooled Water Confined in a Silica Xerogel: Temperature and Pressure Dependence of Boson Peak and of Mean Square Displacements

2013

A silica xerogel can be obtained from an alcoxide precursor (TMOS, tetramethylortosilcate) via the sol-gel method: TMOS hydrolysis and subsequent polycondensation yields a solid, disordered, porous SiO2 matrix (average pore dimensions ~20Å). Inside the pores water is trapped and the hydration level h=gr[H2O]/gr[SiO2] can be easily controlled. The presence and temperature dependence of the boson peak (BP) in xerogel confined supercooled water was studied with inelastic neutron scattering (spectrometer IN6 at ILL, Grenoble) in xerogel samples having h=0.4 and h=0.2. After careful subtraction of the contributions arising from the matrix and from quasi-elastic scattering, the BP contribution wa…

silica xerogel boson peak inelastic neutron scattering excess density of states LDL->HDL transition mean square displacements elastic neutron scattering protein dynamical transitionSettore FIS/07 - Fisica Applicata(Beni Culturali Ambientali Biol.e Medicin)
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Flat-band superconductivity in strained Dirac materials

2016

We consider superconducting properties of a two-dimensional Dirac material such as graphene under strain that produces a flat band spectrum in the normal state. We show that in the superconducting state, such a model results in a highly increased critical temperature compared to the case without the strain, inhomogenous order parameter with two-peak shaped local density of states and yet a large and almost uniform and isotropic supercurrent. This model could be realized in strained graphene or ultracold atom systems and could be responsible for unusually strong superconductivity observed in some graphite interfaces and certain IV-VI semiconductor heterostructures.

superconducting propertiesMaterials sciencesuprajohtavuusDirac (software)FOS: Physical sciences02 engineering and technology01 natural scienceslaw.inventionsuprajohteetSuperconductivity (cond-mat.supr-con)Condensed Matter::Materials SciencelawUltracold atompuolijohteetCondensed Matter::Superconductivity0103 physical sciencesgrafeeniGraphite010306 general physicsSuperconductivityLocal density of statesCondensed matter physicsta114Dirac materialsGrapheneCondensed Matter - SuperconductivityIsotropySupercurrent021001 nanoscience & nanotechnology0210 nano-technologyPhysical Review B
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Field dependence of the vortex-core sizes in dirty two-band superconductors

2019

We study the structure of Abrikosov vortices in two-band superconductors for different external magnetic fields and different parameters of the bands. The vortex core size determined by the coherence lengths are found to have qualitatively different behaviour from that determined by the quasiparticle density of states spatial variation. These different vortex core length scales coincide near the upper critical field, while the discrepancy between them becomes quite significant at lower fields. Within the diffusive approximation we demonstrate several generic regimes in the field dependence of the vortex core sizes determined by the disparity of diffusion constants in the two bands.

suprajohtavuusmultiband superconductivityFOS: Physical sciences02 engineering and technology01 natural sciencessuprajohteetSuperconductivity (cond-mat.supr-con)disordered systemsCondensed Matter::Superconductivity0103 physical sciences010306 general physicsCritical fieldPhysicsSuperconductivityCondensed matter physicsCondensed Matter - Superconductivityvortices in superconductors021001 nanoscience & nanotechnologycoherence lengthMagnetic fieldVortexScattering ratePairingDensity of statesQuasiparticle0210 nano-technology
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Isophorone on Au/MgO/Ag(001) : Physisorption with Electrostatic Site Selection

2017

We report a computational study of isophorone C9H14O adsorption on a Ag(001)-supported ultrathin MgO film with Au adatoms and clusters employing density functional theory calculations. The calculations show that the keto form of isophorone is more stable than the enol tautomers both in gas phase and on the MgO/Ag(001) surface. The interaction between the keto isophorone and step and terrace sites of MgO/Ag(001) displays long interaction distances, relatively weakly exothermic adsorption energies, lack of charge transfer, and minor changes in the density of states, all of which indicate that the molecule merely physisorbs on the surface. The step sites are energetically preferred adsorption …

ta114Chemistry02 engineering and technology021001 nanoscience & nanotechnologyPhotochemistry01 natural sciencesTautomerEnolSurfaces Coatings and FilmsElectronic Optical and Magnetic Materialschemistry.chemical_compoundCrystallographyGeneral EnergyAdsorptionPhysisorptionisophorone adsorption0103 physical sciencesDensity of statesMoleculeDensity functional theoryPhysical and Theoretical Chemistry010306 general physics0210 nano-technologyta116IsophoroneJournal of Physical Chemistry C
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The Role of the Anchor Atom in the Ligand of the Monolayer-Protected Au25(XR)18– Nanocluster

2015

We present a density functional theory (DFT) investigation on the role of the anchor atom and ligand on the structural, electronic, and optical properties of the anionic Au25(XR)18– nanocluster (X = S, Se, Te; R = H, CH3, and (CH2)2Ph). Substituting the anchor atom with other group 16 elements induces subtle changes in the Au–Au and Au–X bond lengths and polarization of the covalent bond. The changes in the electronic structure based on substituting both the anchor and R groups are presented through careful analysis of the density of states and theoretical determined optical spectra. We give a detailed side-by-side comparison into the structural, electronic, and optical properties of Au25(X…

ta114LigandChemistryligandsElectronic structureanchor atomsSurfaces Coatings and FilmsElectronic Optical and Magnetic MaterialsBond lengthCrystallographyGeneral EnergyCovalent bondComputational chemistryAtomMonolayerDensity of statesDensity functional theoryPhysical and Theoretical Chemistryta116gold nanoclustersJournal of Physical Chemistry C
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Dirakův kužel a pseudogapped hustota stavů v topologické polovině Heuslerovy sloučeniny YPtBi

2016

Topologické izolátory (Tis) jsou zajímavé materiály, které vykazují nebývalé vlastnosti. . Zde jsme prozkoumali sloučeniny YPtBi jako příklad ze třídy polovu-Heuslerových materiálů. Topological insulators (TIs) are exciting materials, which exhibit unprecedented properties, such as helical spinmomentum locking, which leads to large torques for magnetic switching and highly efficient spin current detection. Here we explore the compound YPtBi, an example from the class of half-Heusler materials, for which the typical band inversion of topological insulators was predicted. We prepared this material as thin films by conventional cosputtering from elementary targets. By in situ time-of-flight mo…

topologické izolátoryPhysicsCondensed matter physicsSpintronicsFermi energy02 engineering and technologyengineering.materialSpin current021001 nanoscience & nanotechnologyHeusler compound01 natural sciencesDirac conetopological insulatorsHeuslerovy slitinyTopological insulator0103 physical sciencesHeusler alloysengineeringDensity of statesCondensed Matter::Strongly Correlated ElectronsThin film010306 general physics0210 nano-technologyPhysical Review B
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